1. Field of the Invention
The present invention relates to a structure of a pile head joint portion for joining a pile head of a pile body and an upper structure, and a pile head fitting tubular body for fitting the pile head.
2. Description of the Prior Art
In the case of constructing an upper structure such as a bridge pier, a floor board, a building or the like on a head portion of the pile head, it is necessary to join the upper structure to the pile head.
The structure of the conventional pile head joint portion is formed by constructing a bottom board by a cast-in-place concrete in such a manner as to dig the pile head portion into the bottom board of the upper structure at a level of 10 cm to a diameter of the pile, after driving a precast pile and constructing a cast-in-place pile. In this case, in order to secure a strength of the pile head portion, a reinforcing bar is protruded into the bottom board from an end portion of the pile head, and the protruding reinforcing bar is reinforced by surrounding by a loop-shaped and spiral-shaped reinforcing bar. Further, as shown in Japanese Unexamined Patent Publication No. 9-21141, there is a construction method of integrally forming a pile and a box body by fitting the pile head to the steel box body provided with an opening portion for fitting the pile head therein after building group piles and casting the concrete into the box.
Further, as a construction method of constructing a cast-in-place pile and an embedded pile having a small bore diameter equal to or less than 30 cm (hereinafter referred to as a micro pile a), there is a micro pile construction method. The micro pile construction method is a construction method of piercing a steel tube (a casing) b into a supporting ground g while drilling a hole by a boring machine, inserting a reinforcing screw reinforcing bar d or the like into the steel tube b, and thereafter charging a grout c such as a cement milk, a mortar or the like. Further, in order to improve a pull-out resistance of the pile, a push-out shear resistance of the bottom board and the like, the micro pile a and the bottom board f are integrally formed by mounting a bearing plate e to the pile head portion, and thereafter casting in place the concrete of the bottom board f (refer to FIG. 6).
In the conventional structure of the pile head joint portion mentioned above, the following problems are generated.
(a) The reinforcing bar in the board supporting the upper structure, the reinforcing bar protruding from the pile head portion and the reinforcing bar reinforcing the same are complicated, or the bearing plate provided in the pile head portion is in the way, whereby it is hard to securely charge the concrete to the pile head joint portion, so that it is hard to secure a quality of the pile head joint portion.
(b) After constructing the pile body, since the upper structure is constructed by the cast-in-place concrete after processing the pile head portion, it is hard to shorten the process. Further, in the case of constructing the pile body in accordance with the micro pile construction method, the process required for constructing the pile body is shorter than the general pile body construction, however, since the bottom board is constructed by the cast-in-place concrete, it is hard to greatly shorten the process required for all of the construction of the pole and the bottom board.